Organic Light-Emitting Diode (OLED) display devices are widely used in MP3 players and the like digital products due to their characteristics of light weight, thin profile, energy-saving, etc. The OLED display technology differs from the conventional LCD (Liquid Crystal Display) display technology, it does not need a backlight module and typically adopts very thin organic material films and a glass substrate, and these organic materials will emit light when a current passes through them. Moreover, an OLED display screen can be made-lighter, thinner, and capable of saving electric energy remarkably, and have wider viewing angles. However, as a display device, the OLED display screen is also affected by an external use environment. Especially in an outdoor, strong-light environment, display effect of the OLED display screen will be degraded to some extent.
In order to overcome the influence of ambient light, as shown in FIG. 1, an OLED display structure has been proposed, and it eliminates the influence of strong ambient light on the display by providing a quarter-wave plate layer 60 and a linearly polarizer layer 70 on an OLED pixel layer 20 in sequence. Its operational principle will be described below. Ambient light 80 is incident into a display screen, and is changed to linearly polarized light after it passes through the linearly polarizer layer 70 firstly, and then the linearly polarized light passes through the quarter-wave plate layer 60 (an optical axis of which is at an angle of ±45° with respect to the polarization direction of the linearly polarized light) to change to right-handed or left-handed circularly polarized light. That is, the linearly polarizer layer 70 and the quarter-wave plate layer 60 work in combination as a right-handed or left-handed circular polarizer, which can convert natural light into right-handed or left-handed circularly polarized light. The right-handed or left-handed circularly polarized light is changed into left-handed or right-handed circularly polarized light, for example, after it is reflected by a substrate 10, and is further changed to linearly polarized light again after it passes through the above quarter-wave plate layer 60 for the second time, but its polarization direction is rotated by 90° to exactly coincide with the absorption axis of the linearly polarizer layer 70. Thereby, the reflected light is absorbed by the linearly polarizer layer 70 and cannot be transmitted therethrough. That is, right-handed circularly polarized light cannot pass through a left-handed circular polarizer, or left-handed circularly polarized light cannot pass through a right-handed circular polarizer. Therefore, with the above configuration, such objects that the influence of ambient light is eliminated, contrast is enhanced, and visual effect is improved can be achieved.
However, light emitted by the OLED pixel layer 20 have no polarization characteristics, and still does not possess polarization characteristics yet after it is transmitted through the quarter-wave plate layer 60, while their energy is absorbed in half upon passing through the linearly polarizer layer 70. Further due to influence factors like scattering, reflection and so on, the transmittance of light is greatly reduced. This results in the consequence that, in order to obtain suitable brightness, pixel currents have to be increased in practice. In turn, this brings about waste of energy.